1. Field of the Invention
The present invention relates to a process for attaining a production-run state in a web-fed rotary printing machine having a form cylinder and an inking mechanism with inking zones. The inking mechanism has an ink duct box as well as ink transfer rollers and ink application rollers, which ink the form cylinder by zones in accordance with an image to be printed on a printing stock web.
2. Description of the Related Art
In sheet-fed offset printing machines, a process to reduce the number of spoiled sheets at the start of printing is known. Before any paper is printed on, ink application rollers and a wetting agent application roller are positioned on a form cylinder. Without using any paper, it is possible to achieve a desired ink flow from an ink duct box to the surface of the form cylinder as well as a desired supply of wetting agent to the surface of the form cylinder. Water quantity and printing ink quantity are regulated by suitable servocontrol, taking into account a lack of pressure, at the moment. Thus, less water and less printing ink are taken by the form cylinder and from the wetting agent application roller than would be taken during a production run.
In known rotary printing machines, the above process cannot be implemented without further measures, due to the uninterrupted printing stock web, which is transported by means of contact between printing cylinder and the form cylinder (direct printing), or contact between printing cylinder and a transfer cylinder, i.e., a rubber-blanket cylinder (offset printing). Because of the contact of the printing stock web with the form cylinder or the rubber-blanket cylinder, starting and stopping the paper transport is problematic. Disadvantageously the paper web adheres to the form cylinder or rubber-blanket cylinder due to friction, especially as a result of ink residues. Therefore, the paper web is damaged. Furthermore, web tears cannot be ruled out.
In addition, in rotary printing machines that use a wetting agent, it has been found that ink zone blades that rest on the ink duct roller are set to a gap width of 0 upon interruptions in production and at the end of production. The printing ink located on the ink application roller (which has already been moved away from the form cylinder) and the ink transfer rollers, is thereby conveyed back to the ink duct roller by the ink feed roller. The printing ink is consequently emulsified with the wetting agent, and because of enrichment with the wetting agent in the inking mechanism, impurities are fed back to the ink duct box. On the other hand, if, when the ink zone blades are set to a gap width set at 0, an attempt is made to transfer the ink remaining in the inking mechanism from the ink transfer rollers and the ink application roller positioned on the form cylinder to the form cylinder, i.e., to the printing forms located thereon, while at the same time moving the wetting mechanism out of position, an acute danger of a printing web breakage is created.
German reference DE 44 30 693 A1 discloses a rotary offset printing machine in which the form cylinder, the transfer cylinder and the pressure cylinder have separate individual drives and are not in mechanical driving connection with one another. Similarly, the rollers of an inking mechanism or a wetting mechanism can be driven separately from the form cylinder, the transfer cylinder or the pressure cylinder. For example, all ink and wetting agent distribution cylinders of an inking mechanism and a wetting mechanism can have a shared drive with an electric motor. The wetting agent distribution cylinder could also be driven by a separate electric motor, however. Further, German reference DE 44 30 693 A1 discloses a rotary printing machine wherein, each ink and wetting agent distribution cylinder is driven by a separate electric motor.